/Engine/Plugins/Runtime/XRBase/Source/XRBase/Public/HeadMountedDisplayFunctionLibrary.h
Returns true, if HMD is in low persistence mode. 'false' otherwise.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintPure, Category="Input|HeadMountedDisplay", Meta=(DeprecatedFunction, DeprecationMessage="This functionality is no longer available. HMD platforms that support low persistence will always enable it.")) static bool IsInLowPersistenceMode()